This invention relates to a method of manufacturing improved mold inserts. Mold inserts of the type to which this invention pertains are used in machines for injection molding plastic workpieces, but this invention may be useful in other fields, such as die casting and rubber molding.
This invention is disclosed for use with mold inserts of the type shown in my U.S. Pat. No. 4,828,479, granted May 9, 1989, and U.S. Pat. No. 4,959,002, granted Sep. 25, 1990, the disclosures of which are hereby incorporated by reference herein. (The '479 and the '002 patents are hereinafter referred to as "said patents".) Said patents disclose generally cylindrical mold inserts for injection mold machines which have a generally cylindrical liquid channel section with a liquid conduit groove extending circumferentially around the liquid channel section. A liquid barrier is located in the groove so that the groove is double-ended, one end constituting a liquid inlet end and the other end constituting a liquid outlet end. A mold machine with which an insert is used has inlet and outlet connectors aligned with the inlet and the outlet ends of the groove so that a liquid, which is usually water, can be circulated around the insert for cooling or heating portions of the insert.
The mold inserts to which said patents relate are used in matched pairs, one being mounted on an "A" plate of an injection molding machine and the other mounted on its confronting "B" plate. Proper orientation of inserts on their respective "A" and "B" plates is maintained by interfitting keys and notches. The liquid inlets and outlets for both the "A" and the "B" plates are usually located on the same side of a master frame. If one were able to look at the liquid barriers of a pair of mutually confronting inserts from the outside of a master frame, both liquid barriers would appear to be on the same side of the master frame. However, one looking at the "A" plate insert from its front face would observe that its liquid barrier is on one side of the insert and, upon looking at the "B" plate insert from its front face, would observe that its liquid barrier is on the opposite side. Thus, for example, if the liquid barrier of the "A" plate insert is located at the 3:00 o'clock position, as viewed from the front face of the insert, then the liquid barrier on the "B" plate insert would be at the 9:00 o'clock position, as viewed from its front face.
Until machined to form the shapes of the mold cavities and cores, the only difference between an insert usable with an "A" plate of a mold machine and one usable with a "B" plate for the same machine is in regard to the location of the inlet and outlet barrier. This difference creates an inventory problem for a supplier of inserts. The practice has been to inventory inserts without the barriers and to weld dams that form the barriers into the liquid grooves when the inserts are removed from inventory for use or sale. The welding operations must be carried out with care, not only to insure that each dam is installed in the proper location, but also to insure that a dam will not, during use, slide or otherwise move around in the liquid conduit groove and will not work loose while the insert cavity or core is being machined. (The machining operations are usually done, at least in part, on turning lathes which rotate the inserts at high speeds and there is a danger that a loose dam would fly away from a rotating insert and cause injury to the lathe operator.) The use of the described welding procedure is obviously inefficient and costly because it requires the availability of a skilled welder when each insert is removed from inventory in order to insure that a liquid barrier is properly formed. Of course, an option would be to inventory inserts having inlet and outlet barriers already formed. However, that would require twice the inventory to reasonably insure that there would be an adequate supply of inserts usable with "A" plates and also an adequate supply of inserts usable with "B" plates.
The user of a mold insert often drills liquid passageways extending inwardly from circumferentially-extending liquid conduit grooves to meet various cooling or heating needs. To insure an adequate flow of liquid into such inwardly directed passageways, one or more additional dams or barriers are affixed inside the peripheral liquid conduit groove. The provision of additional dams or barriers, using the present welding procedures, can be time consuming and costly.
Accordingly, there exists a need to improve the efficiency with Which inserts can be inventoried and there is also a need to enable the user of an insert to quickly, accurately and securely assemble liquid dams or barriers into liquid conduit grooves of mold inserts.